Battery diaphragm

• US 6,461,772 B1
• Filed: 12/14/1999
• Issued: 10/08/2002
• Est. Priority Date: 12/14/1998
• Status: Expired due to Term

• Current Assignee: Kansai Electric Power Company Incorporated, Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Original Assignee: Kansai Electric Power Company Incorporated, Sumitomo Electric Industries Limited (Sumitomo Corporation)
• Inventors: Miyake, Shinichi, Tokuda, Nobuyuki
• Primary Examiner(s): Chaney, Carol
• Assistant Examiner(s): YUAN, DAH WEI D
• Application Number:
  US09/460,808
• Time in Patent Office: 1,029 Days
• Field of Search: 429/245, 429/246, 429/247, 429/249, 429/253, 429/254
• US Class Current: 429/247
• CPC Class Codes: H01M 50/426 Fluorocarbon polymers
• CPC Class Codes: H01M 50/44 Fibrous material
• CPC Class Codes: H01M 50/457 comprising three or more layers
• CPC Class Codes: H01M 50/491 Porosity
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

A battery diaphragm having superior chemical resistance, low resistance, superior ion selective permeability and high mechanical strength is provided. The battery diaphragm is formed of a composite film including a complex of a porous base substrate (A) with a crosslinked polymer (B₁) containing repeated units of a vinyl heterocyclic compound having at least two hydrophilic groups. Alternatively, the battery diaphragm is formed of a composite film including a complex of a porous base substrate (A) with a crosslinked polymer (B2) containing repeated units of a vinyl compound each having a functional group, and thereafter decomposing part of the functional groups. Alternatively, the battery diaphragm is formed of a composite film including a complex of a porous base substrate (A) with a crosslinked polymer (B3) containing repeated units of a vinyl compound each having a functional group, wherein the complex of the porous base substrate (A) with the crosslinked polymer is prepared by impregnating a porous structure of the porous base substrate (A) with a monomer mixture containing a crosslinking momomer and the vinyl compound having functional groups, and thereafter causing photopolymerization to generate the crosslinked polymer (B3) in the porous structure.

Claims

1. A battery diaphragm formed of a composite film comprising a complex of a porous base substrate with a crosslinked copolymer, the crosslinked copolymer is prepared by impregnating a porous structure of the porous base substrate with a monomer mixture comprising a crosslinking monomer and at least one vinyl compound having functional groups, and causing polymerization to generate the crosslinked copolymer in the porous structure.

2. The battery diaphragm according to claim 1, wherein the crosslinked polymer contains repeated units of a vinyl heterocyclic compound having at least two hydrophilic groups.

3. The battery diaphragm according to claim 2, wherein the porous base substrate is a polytetrafluoroethylene porous film.

4. The battery diaphragm according to claim 2, wherein the heterocyclic compound is at least one compound selected from the group consisting of 1-vinylpyrrolidone and vinyl imidazoles.

5. The battery diaphragm according to claim 4, wherein the porous base substrate is a polytetrafluoroethylene porous film and the monomer mixture comprises 1-vinyl imidazole, 4-vinyl pyridine and divinyl benzene.

6. The battery diaphragm according to claim 5, wherein the monomer mixture contains 1 to 60 wt % of 1-vinyl imidazole, 20 to 80 wt % of 4-vinyl pyridine, and 10-50 wt % of divinyl benzene.

7. The battery diaphragm according to claim 4, wherein the porous base substrate is a polytetrafluoroethylene porous film and the monomer mixture comprises 1-vinyl pyrrolidone, 4-vinyl pyridine and divinyl benzene.

8. The battery diaphragm according to claim 7, wherein the monomer mixture contains 20 to 60 wt % of 1-vinyl pyrrolidone, 20 to 60 wt % of 4-vinyl pyridine, and 10 to 50 wt % of divinyl benzene.

9. The battery diaphragm according to claim 1, wherein the crosslinked copolymer contains a vinyl compound having a hydrolyzable functional group, and thereafter, hydrolysis of hydrolyzable functional group and generation of hydroxyl group after polymerization.

10. The battery diaphragm according to claim 9, wherein the porous base substrate is a polytetrafluoroethylene porous film.

11. The battery diaphragm according to claim 9, wherein the crosslinked copolymer contains a vinyl compound having a hydrolyzable functional group and a vinyl compound having an anion-exchange group.

12. The battery diaphragm according to claim 9, wherein the monomer contains 4-vinyl pyridine, vinyl acetate and divinyl benzene.

13. The battery diaphragm according to claim 12, wherein the monomer mixture contains 50 to 80 wt % of 4-vinyl pyridine, 1-80 wt % of vinyl acetate, and 10-50 wt % of divinyl benzene.

14. The battery diaphragm according to claim 9, wherein the monomer mixture contains 4-vinyl pyridine, vinyl propionate or vinyl-n-butyrate, and divinyl benzene.

15. The battery diaphragm according to claim 14, wherein the monomer mixture contains 50 to 80 wt % of 4-vinyl pyridine, 1-30 wt % of vinyl propionate or vinyl-n-butyrate, and 10 to 50 wt % of divinyl benzene.

16. The battery diaphragm according to claim 1, wherein the crosslinked copolymer is generated by photopolymerization.

17. The battery diaphragm according to claim 16, wherein the base substrate is a polytetrafluoroethylene porous film.

18. The battery diaphragm according to claim 17, wherein the polytetrafluoroethylene porous film as the porous base substrate has a porosity of 70 to 85% and a thickness of 20 to 60 μ

m.

19. The battery diaphragm according to claim 16, wherein the vinyl compound of the crosslinked copolymer is a vinyl compound having an anion-exchange group.